Occasional rough idle, anyone else?

[SL8888]

You can fix that with a lighter flywheel and 0 Weight motor oil.

I'm thinking that the RPM issue has something to do with the computer. If you lift off the accelerator in my 69 Vett with the manual gear box (12 to 1 compression motor), you are going to move forward toward the windshield. GT-350 its like you lift slowly off the accelerator. Just thinking......

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[Rusherific]

I'm thinking that the RPM issue has something to do with the computer. If you lift off the accelerator in my 69 Vett with the manual gear box (12 to 1 compression motor), you are going to move forward toward the windshield. GT-350 its like you lift slowly off the accelerator. Just thinking......

Yeah I'm pretty sure it's the ETB which is an issue with most modern cars. Sport mode helps a bit but then you get that artificial throttle mapping, I figured that out right away as the car wouldn't even slow down off throttle when I'm trying to break the damn thing in! But it's clear the car is tuned around town to be, gentle shall we say.

 

[honeybadger]

FWIW, my car used to do this. The race motor and aftermarket tune eliminated it, though. I wouldn’t worry about it

 

[Rusherific]

FWIW, my car used to do this. The race motor and aftermarket tune eliminated it, though. I wouldn’t worry about it

Yeah I figure as much especially seeing it seems to be common around here, just wanted to make sure it wasn't a sign of something deeper! It's definitely not unlivable or anything

 

[JR369]

I'm thinking that the RPM issue has something to do with the computer. If you lift off the accelerator in my 69 Vett with the manual gear box (12 to 1 compression motor), you are going to move forward toward the windshield. GT-350 its like you lift slowly off the accelerator. Just thinking......

The two times it happened to me it seemed like the throttle was very responsive in that when I lifted off the pedal the needle drop was very fast and fell below normal idle and it just stumbled a bit to get back to normal idle. I have never reproduced it since so I do not worry about it. I was in Sport mode btw. I always drive it in Sport mode. It is more responsive.

 

[SL8888]

I always drive in Track mode, the car gets "Angry"
I flip the exhaust to quiet if necessary.....

 

[Rusherific]

I always drive in Track mode, the car gets "Angry"
I flip the exhaust to quiet if necessary.....

I haven't even tried track yet. I figure gotta leave stones unturned to keep it interesting....

 

[DIB2016]

It's is totally normal. On my 3rd Gt350 and they all have done it.

 

[MGT350]

I tried searching and couldn't find much. This is a very recent thing that I've only noticed starting a few weeks ago (1k miles before without this issue). I'm pretty sure it only happens once temps are up and the engine goes down to its lowest idle, sometimes at a stop light, after a few seconds of smooth idling it will noticeably dip down in rpms just a little, and start to get a little shaky, to where you can hear and feel the engine stumbling a bit. It only happens maybe once or twice a drive, sometimes more often than that, sometimes never in a single drive. And so far hasn't caused any actual driving problems yet. No warning lights or anything. I wouldn't call it a full on miss but you can feel the car shake a little when it's doing it.

Just curious if anyone else has had this absent any other problems?

Check the pins for the camshaft position sensor plugs on top of the valve covers and make sure they plug in properly. The dealer replaced mine and idle issue fixed.

 

[Reddirocket27]

Happens to me, like clockwork, when I fill up. Must be the charcoal canister or something having to do with the system bc there's a LOT on google about your exact symptoms. Seems to be a $40 evap line. I usually only fill up to 90% now to avoid the "stumble". Always drives fine, but that idle cough and wheeze gets super old.

 

[Rusherific]

Check the pins for the camshaft position sensor plugs on top of the valve covers and make sure they plug in properly. The dealer replaced mine and idle issue fixed.

Are those the 2 plugs on each side toward the front of the covers? They looked secure after my last drive but should I try re-seating them this weekend?

 

[Rusherific]

Happens to me, like clockwork, when I fill up. Must be the charcoal canister or something having to do with the system bc there's a LOT on google about your exact symptoms. Seems to be a $40 evap line. I usually only fill up to 90% now to avoid the "stumble". Always drives fine, but that idle cough and wheeze gets super old.

Interesting but I'm worried it might be worse than just an occasional idle thing, like when this all started happening the sound of the engine definitely changed during street driving, and it feels like the car doesn't really "wake up" until I drive it hard and feels more like it used to/should. It's hard because that aspect of it could all be in my head, but combined with the fuel/evap system explanation people are giving me has me wondering if it is in fact real and related. Is it possible I got some bad gas maybe that's plugged something up? And if I do a few WOT accelerations it clears up?

 

[MGT350]

Are those the 2 plugs on each side toward the front of the covers? They looked secure after my last drive but should I try re-seating them this weekend?

So did mine. It is a common probelm. Take it to the dealer and let them scan it.

 

[MLM54]

I tried searching and couldn't find much. This is a very recent thing that I've only noticed starting a few weeks ago (1k miles before without this issue). I'm pretty sure it only happens once temps are up and the engine goes down to its lowest idle, sometimes at a stop light, after a few seconds of smooth idling it will noticeably dip down in rpms just a little, and start to get a little shaky, to where you can hear and feel the engine stumbling a bit. It only happens maybe once or twice a drive, sometimes more often than that, sometimes never in a single drive. And so far hasn't caused any actual driving problems yet. No warning lights or anything. I wouldn't call it a full on miss but you can feel the car shake a little when it's doing it.

Just curious if anyone else has had this absent any other problems?

@Rusherific did you ever get this figured out? Very similar issue with mine recently and wondering if any of the recommended fixes worked.

Thanks

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